Intense red photoluminescence and mechanoluminescence from Mn2+-activated SrZnSO with a layered structure

A series of novel red emitting Mn2+-activated SrZnSO phosphors were successfully synthesized by solid-state reaction at high temperature. The photoluminescence (PL) and mechanoluminescence (ML) properties of these Mn2+-activated SrZnSO phosphors with different Mn2+ concentrations were investigated. With increasing the concentration of Mn2+ from x = 0 to 0.04, the unit cell volume increased from 153.82 to 154.19 Å3 while the optical band gap decreased from 3.74 to 3.43 eV. The site occupation of Mn2+ in the host lattice was demonstrated by Rietveld refinement, the electron paramagnetic resonance (EPR) spectrum, and the spectroscopic properties. A broad band emission peak at 603 nm of SrZn1−xMnxSO (0.001 ≤ x ≤ 0.04) with an excitation wavelength of 318 nm was attributed to electronic transitions of Mn2+ from the 4T1(4G) level to the 6A1(6S) level. The lifetime of SrZn1−xMnxSO (0.001 ≤ x ≤ 0.04) decreased monotonously from 2.97 to 0.82 ms with increasing Mn2+ concentration. In particular, intense emission of red light from SrZn1−xMnxSO (0.001 ≤ x ≤ 0.04) under compressive load could be observed even with the naked eye, indicating that SrZn1−xMnxSO could be used for stress sensors or stress imaging. There was a linear correlation between the ML intensity and external load in SrZn1−xMnxSO, and the ML intensity could be recovered under UV light irradiation. Considering its advantages of non-destruction, reproducibility, and high ML intensity, SrZn1−xMnxSO might be useful for non-destructive detection of stress.